U.N Secretary General Ban Ki-Moon, center. receives flowers from a girl upon his arrival at Nnamdi Azikiwe International airport in Abuja, Nigeria Sunday, Aug. 23, 2015. U.N. Secretary General Ban Ki-moon arrived in Nigeria Sunday to mark the Boko Haram bombing of his organization’s headquarters and focus new attention on 219 schoolgirls held by the extremist group. (AP Photo/Gbemiga Olamikan)

UNICEF says attacks by armed extremist group Boko Haram have forced 500,000 children to flee their homes in the last five months.

The U.N.’s children agency says 1.4 million children overall are “on the run” in Nigeria and neighboring countries where the group has sown terror in recent months. More than half of the 1.2 million children who have fled northern Nigeria alone are under 5 years old.

Spokesman Christophe Boulierac says the agency is in “full operational mode” in the region but has received less than one-third of the $50 million funding it has sought for the Lake Chad region.

Speaking Friday at a U.N. news conference in Geneva, Boulierac also appealed for renewed attention on the 219 girls abducted in April 2014 from a school in Chibok.